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GTC Solar Water Heater - Evacuated Tubes - 14 years later


New Member
Jan 20, 2024
Huntsville Alabama
Good Morning. I installed a two GTC Manifolds with 30 Evacuated Tubes, an 80 Gallon Collector and controller back in 2010. After inspecting the system due to a leak coming from my attic there were a few discoverys made which lead me down the current path to remove my system and consider relocating the tubes to the ground for easier access or sell the system and say goodbye to my solar days.

In the beginning...The system when first installed was phenomenal. Water temps in the collector were typically very high (+150F) on good days. Over the years I noticed a dramatic decrease in temps. They gradually dropped and I rarely saw temps over 80 F. This system was rarely checked on the roof with the occasional visual inspection. The closed loop was periodically purged every year or so. I recently swapped the closed loop fluid with clean new freeze protected fluid.

1st Issue:
I started noticing pressures of 20-60 psi in my closed loop. Typically around 20 psi the pump would kick on an cycle the CL Fluid from the roof to the tank and the pressure would decrease as the line temp decrease. This was not the case. The pressures stayed very high!

Winter Freeze:
After a few solid days of 5-10 degrees F and then a thaw I found a burst Closed Loop pipe going to the roof. This was diagnosed to a corroded copper heat exchanger tube in the 80 gallon collector. Potable water mixed with my 2 gal closed loop glycol and eventually froze and burst. Hense the high pressure. The pressure I was seeing was street water pressure feeding into my closed loop. Not Good.

I decided to pull the evacuated tubes and manifold off the roof. A new discovery was made. Each on of my heat pipes inside the evacuated tubes had burst and split at the lower end of the copper HP. No, my system was not engaged to cycle from the collector to the roof on days with freezing temps. This could have prevented damage to each of the heat pipes.

I am in the process of repairing each of the HP and experimenting with fluid, fluid quantities and proper vacuum.

These systems are not designed for turnkey operations. They are highly technical and work wonderfully when used correctly. If you have a system installed and live anywhere that can experience freezing temperatures, please don't forget to set your controller to cycle fluid it outside temperatures reach 32F or below. It will save you some hassles.

My question to the community is this. Is there a market for used Solar Water Heaters. I purchased a new 80 Gallon Tank, another 60 Tube Manifold and still have my original 2 each 60 Tube Manifolds, controller, copper plumbing, etc. Just not sure I need to reinstall given my low hot water needs now that my kids have flown the coop. Where would I even begin to sell?


Can only speak for the UK, the market for new Solar Water Heaters has disappeared due to the huge drop in price of PV panels, which can be used to feed an electric immersion heater for hot water and relatively fault free in comparison. Market for used ones is even less, the copper content may get you more from the scrap merchant.

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